This is the only version of The Sign of the Four written in Gregg Shorthand. This book was first published between July 1915 and July 1916 (Publishers' Weekly American Educational Catalog of 1916). The shorthand plates written by Alice Rinne Hagar match the 1902 Pre-Anniversary Gregg Shorthand Manual.
This book is listed in a March 1916 printing of the 1902 Gregg Shorthand Manual. The 1916 Gregg Shorthand Manual replaced the 1902 Manual. The 1916 Manual was published in June 1916. A review of the shorthand in this book clearly indicates that it matches the 1902 Gregg Shorthand Manual.